Hiya Claire and welcome.
I can't imagine that Burl has not visited the circle but I guess the producer should have done his homework and checked his Wainwright.
If you can't see it (& I don't doubt you!) I suspect that the most likely thing is that Mr B ws mistaken - either in identifying the hills, or in putting the book together.
It certainly seems impossible that he wouldn't've been to such a famous circle!